This research extends previously published studies on the biology and in vitro immunity of cultured colon tumor cells. After establishing a set of characterized human colon cancer cell lines (LS180, L174T, and their clones) exhibiting malignant properties and reflecting characteristics of the original tumor, we produced a series of monoclonal antibodies (Mab) against LS174T tumor cells, of which 5E113 is selective for human colon cancer. Partially purified tumor antigens bind 5E113 in ELISA assay and competitively block antibody binding to the tumor cell. An in vitro system has been developed to study immunogenicity of tumor antigens. Research will test the hypothesis that internal image anti-idiotypic (Id) antibodies produced against Mabs such as 5E113 represent mirror images of the antigen-combining site of the original 5E113 antibody, mimicking the colon tumor antigen. The specific aims are to: (1) produce Id antibodies toward Mab reactive with human colon cancer; and (2) assess the activity of Id antibodies as antigens in humoral and cell-mediated immune assays. Id antibodies will be produced in one of three alternative host models: (1) New Zealand white rabbits immunized to 5E113 Mab to human colon cancer, followed by affinity column chromatography isolation of Id antibodies; (2) Wistar-Furth rats tolerized to normal BALB/c mouse immunoglobulins prior to immunization with Mab; and (3) normal BALB/c spleen cells immunized in vitro with Mab. Experimental approaches will evaluate the antigenic characteristics of the Id antibodies, including Id antibody binding onto "immune" lymphocytes from colon cancer patients, either from peripheral blood or dispersed from the tumor mass. The immunogenicity of Id antibodies, to determine the range of antigenic activities and elicit responses toward colon tumors, will be tested by: (1) producing antibody and T-cell responses in BALB/c mice directed against LS174T cells tested in vitro; (2) eliciting in vitro secondary immune responses from colon cancer immune murine and human (patient) lymphocytes; and (3) generation of in vitro primary cellular immunity in naive BALB/c and human lymphocytes to human colon cancer antigens. If the Id antibody is found to serve as an effective colon tumor antigen, further studies to evaluate immunodiagnostic and immunotherapeutic protocols in patients will be warranted. (IT)